In process industries such as petroleum (oil) refineries and petrochemical plants, it is a common practice to burn the exhaust gases of a stage of the refinery or plant with a steam-assisted, combustible gas assisted or air assisted flare tip before releasing them to the atmosphere in order to reduce the environment pollution in a process generally referred to as “flaring” or “flare”. Flaring is generally performed only as a year-end process for several weeks up to about one month. More generally, flaring as commonly used in the petrochemical and oil industry is a volatile organic compound (VOC) combustion process used to safely dispose of flammable waste gases from emergency process upsets as well as during process start-up, process shut-down and turnaround operations. Flaring helps prevent the release of toxic hydrocarbons into the atmosphere. However, combustion of hydrocarbons is seldom 100% complete leading to back smoke (hereafter “smoke”) production due to inefficient combustion of the hydrocarbons which can result in significant financial costs due to the burning of valuable hydrocarbons, as well as flare induced noise (or sound) production (either combustion noise or steam injection noise).
Regulatory authorities (e.g., the U.S. Environmental Protection Agency (EPA)) generally impose environmental regulations in terms of monitoring and controlling both smoke and noise. In general smoke reduction has the highest priority, but in locations where the refineries are located relatively close to residential communities, noise reduction can be important too. Failure to adhere to EPA or other regulations can result in the imposition of serious financial penalties and sometime revoking of operating licenses for the owner of the process.
The main role of a flare monitoring and control device or system is to monitor and measure certain parameters of the flare such as amount/volume of the smoke, size of the flare, and noise level (typically in dB), and take certain countermeasures to control the flare so as to ensure compliance with EPA smoke and noise level regulations. A few products and research exists for in-situ and remote sensor-based flare monitoring. For example, systems based on thermocouples, infrared (IR) sensors or a video camera can be used for indicating the presence or absence of smoke and to some extent the quantity of smoke. However, the control action, such as controlling the steam or other assist gas flow to the process to reduce smoke, remains a manual task.